1. Field of the Invention
This invention relates to magnetic recording media of the coating type, for example, various forms of magnetic tape.
2. Background Art
Needle iron oxide is typical of magnetic powders which are used in magnetic recording media. Since needle iron oxide alone cannot accommodate the requirements for higher density magnetic recording, a variety of magnetic materials with high coercivity and enhanced saturation magnetization have been developed.
For example, iron carbide series magnetic powders in which at least the surface is iron carbide are proposed in Japanese Patent Application Kokai (JP-A) Nos. 71509/1985, 124023/1985, 184576/1985, 211625/1985, 212821/1985, 269225/1986, 85403/1987, 86537/1987 and 86531/1987. Also the inventors proposed magnetic powder having a carbon base surface in Japanese Patent Application No. 272057/1991. These magnetic powders are characterized by high coercivity, enhanced saturation magnetization, good conductivity and good light screen.
These prior art approaches, however, do not take into account the dispersion of magnetic powder in a binder and therefore, the magnetic layer is low in packing density and orientation. For example, some of the above-listed patent publications add fatty acids such as lauric acid and stearic acid to magnetic coating compositions as dispersants, but only that means is insufficient in terms of packing density and orientation.